Sustained tissue -specific transgene expression froma vl30 retrotransposon-derived vector in vivo

摘要

Previous attempts to generate transgenic mice via retroviral transduction of pre-implantation embryos have usually not resulted in stable transgene expression. In these cases, inactivation of the retroviral LTR is associated with passage through the germ line. A subset of endogenous murine retrovirus-like retrotransposons (VL30’s) are constitutively expressed in virtually all tissues, with no deleterious effects to the health of the animal. We surmised that these VL30s might be useful as vectors for stable lineage-specific transgene expression. A mouse VL30-derived retro-vector engineered to express a reporter gene (LacZ) was used to generate transgenic mice via transduction of embryonic stem (ES) cells. A single copy of the vector was stably integrated into a unique site in the mouse genome. Sustained tissue specific expression was observed at both the mRNA and protein levels for several generations. Transgene expression was observed in distinct sub-populations of cells in both lung and spleen. In the lung, cells expressing the vector were identified as type II pneumocytes. These data illustrate for the first time that a VL30 LTR (NVL-3) is unique from its retroviral counterparts in that it can pass through the germ line repeatedly without undergoing transcriptional inactivation. Thus, VL30 vectors may be useful for both transgenesis and as alternatives to existing retroviral vectors for gene therapy.